Imaging device and electronic apparatus

ABSTRACT

There is provided an imaging device that includes photovoltaic type pixels that have photoelectric conversion regions generating photovoltaic power for each pixel depending on irradiation light; and an element isolation region that is provided between the photoelectric conversion regions of adjacent pixels and in a state of substantially surrounding the photoelectric conversion region.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/109,865, filed Jul. 6, 2016, which is a national stage applicationunder 35 U.S.C. 371 and claims the benefit of PCT Application No.PCT/JP2015/000129 having an international filing date of Jan. 14, 2015,which designated the United States, which PCT application is acontinuation of and claimed the benefit of U.S. Nonprovisionalapplication Ser. No. 14/567,777, filed Dec. 11, 2014, now U.S. Pat. No.9,373,655, issued on Jun. 21, 2016, and U.S. Provisional ApplicationSer. No. 61/929,842, filed Jan. 21, 2014. This application is also acontinuation of US Nonprovisional application Ser. No. 15/490,683, filedApr. 18, 2017, which is a continuation of U.S. Nonprovisionalapplication Ser. No. 15/148,127, filed May 6, 2016, now U.S. Pat. No.9,659,994; which is a continuation of U.S. Nonprovisional applicationSer. No. 14/567,777, filed Dec. 11, 2014, which claimed the benefit ofU.S. Provisional Application No. 61/929,842, filed Jan. 21, 2014. Thedisclosures of all of these applications and patents are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to an imaging device and an electronicapparatus, and specifically, to an imaging device and an electronicapparatus that can solve a problem such as crosstalk due to a PNjunction diode.

BACKGROUND ART

In the related art, a charge accumulation type imaging device(hereinafter, referred to as an accumulation type imaging device) as animaging device with which an electronic apparatus having an imagingfunction represented by a digital camera is equipped is known.

In the accumulation type imaging device, when excessive light isincident and an accumulation charge amount exceeds a saturation chargeamount, an excess portion of a signal charge flows into an N-typesubstrate beyond an overflow barrier or flows into a floating diffusionbeyond a potential barrier under a transfer gate. Therefore, since adynamic range of the accumulation type imaging device is limited by thesaturation charge amount of a charge accumulation region, it isdifficult to realize a large dynamic range and, as a result, there is aproblem. that overexposure or underexposure is likely to occur.

Thus, as a solid-state imaging device capable of solving such a problem,a log-arithmic sensor configured of photovoltaic type pixels is proposed(for example, see PTL 1 or PTL 2).

FIG. 1 illustrates an equivalent circuit for one pixel of thephotovoltaic type pixel configuring the logarithmic sensor disclosed inPTL 1.

In a photovoltaic type pixel 1, photovoltaic power proportional to alogarithm. of a photocurrent value depending on incident light 2 isgenerated by a PN junction diode 3, the photovoltaic power that isgenerated is amplified by an amplifier 4 and becomes an image signal,and the image signal that is generated is output to a vertical signalline 7 through a switch 6. Moreover, the PN junction diode 3 is reset bya switch 5.

As described above, in the photovoltaic type pixel 1, since the imagesignal that is generated is output to a subsequent stage without beingaccumulated, even when excessive incident light 2 is incident, the pixelsignal is not saturated.

Moreover, the photovoltaic type pixel 1 can be operated as anaccumulation type.

CITATION LIST Patent Literature

PTL 1: EP1354360

PTL 2: US2011/0025898A1

SUMMARY OF INVENTION Technical Problem

However, as a result of analysis of the photovoltaic type pixel 1, thefollowing disadvantages are found.

A first disadvantage is so-called crosstalk. FIG. 2 is a cross-sectionalview illustrating an example of a pixel structure of the photovoltaictype pixel illustrated in FIG. 1 and illustrates an overview of thecrosstalk.

Specifically, when photovoltaic power is generated depending on theincident light 2, the PN junction diode that is a photo-sensor is biasedin a forward direction and, as a result, since electrons diffuse from anN-type region into a P-type substrate, as represented by a dashed arrowline A of FIG. 2, the electrons which are diffused may reach theadjacent photo-sensor (PN junction diode). In this case, since theadjacent pixel is also a photovoltaic type pixel, crosstalk occurs.Moreover, although not illustrated, even if the adjacent pixel of thephotovoltaic type pixel 1 is the accumulation type pixel, crosstalkoccurs similarly.

A second disadvantage is that a change in the pixel signal amount withtemperature is large. A pixel signal voltage V_(PD) can be representedby the following Expression (1).

[Math. I]

V _(PD) =−T In(−f _(S)+1)  (1)

Here, I_(iambda) is the photocurrent, I_(s) is a reverse saturatedcurrent in the PN junction diode 3 and is a value that exponentiallyincreases with increase of the temperature. Thus, when I_(s)exponentially increases with increase of the temperature, the pixelsignal voltage V_(PD) decreases markedly.

The description will be explained in more detail. FIG. 3 illustrates arelationship between illuminance (standardized) of the incident light ateach temperature of the photovoltaic type pixel 1 illustrated in FIG. 1and an output voltage of the PN junction diode 3. It can be understoodfrom FIG. 3 that the generated voltage decreases markedly even at thesame illuminance when the temperature is decreased.

A third disadvantage is that low illuminance sensitivity is low andvariation suppression is difficult. As represented in Expression (1), inorder to increase the sensitivity, it is necessary to lower I. However,it is known that I, is increased by impurity contamination or crystaldefects. However, it becomes costly to suppress all these because ittakes a high degree of process control.

A fourth disadvantage is that when a photovoltaic type pixel 1 operatesas the accumulation type, the dark current is increased.

FIG. 4 illustrates a relationship between irradiation time of thephotovoltaic type pixel 1 and the output voltage (PTL 2, FIG. 2).

A case where the photovoltaic type pixel operates as the accumulationtype corresponds to a linear region of the drawing and the occurrence ofthe dark current can be confirmed.

Description will be given in detail. FIG. 5 is an enlarged view when areverse bias is applied in the vicinity of the photo-sensor (the PNjunction diode 3) of the photovoltaic type pixel 1 illustrated inFIG. 1. When the photovoltaic type pixel 1 is operated as theaccumulation type, the photo-sensor is reverse biased and, in this case,since a depletion layer spreads as illustrated in the drawing and thenan Si/SiO₂ interface is positioned in the depletion layer, the darkcurrent is increased due to influence of the interface state.

The present disclosure is made in view of such a situation and it isdesirable to realize an imaging device which is excellent in lowilluminance sensitivity and low illuminance SIN and of which crosstalkis low while realizing a wide dynamic range.

Solution to Problem

An imaging device according to a first embodiment of the disclosureincludes photovoltaic type pixels that have photoelectric conversionregions generating photovoltaic power for each pixel depending onirradiation light, and an element isolation region that is providedbetween the photoelectric conversion regions of adjacent pixels and in astate of substantially surrounding the photoelectric conversion region.

The element isolation region may be configured of a material that blocksdiffusion of signal charge of the photovoltaic type pixels to theadjacent pixel.

The imaging device that is the first embodiment of the disclosure mayfurther include an accumulation type pixel that is provided adjacent tothe photovoltaic type pixel.

A PN junction diode may be formed in the photoelectric conversion regionas a photo-sensor.

The photovoltaic type pixel may further include a transfer gate andfloating diffusion and may operate as an accumulation type andphotovoltaic type pixel.

The imaging device that is the first embodiment of the disclosure mayfurther include an accumulation type pixel that is provided in aposition adjacent to the accumulation type and photovoltaic type pixel.

The imaging device that is the first embodiment of the disclosure mayfurther include an accumulation type and photovoltaic type pixel havingthe photoelectric conversion region, a transfer gate, and floatingdiffusion, in which the photovoltaic type pixel and the accumulationtype and photovoltaic type pixel may be formed adjacent to each other.

A portion between the photoelectric conversion region and a pixelcircuit region in each pixel is insulated.

An electronic apparatus according to a second embodiment of thedisclosure is an electronic apparatus that is equipped with an imagingdevice, in which the imaging device includes photovoltaic type pixelsthat have photoelectric conversion regions generating photovoltaic powerfor each pixel depending on irradiation light, and an element isolationregion that is provided between the photoelectric conversion regions ofadjacent pixels and in a state of substantially surrounding thephotoelectric conversion region.

In the first and second embodiments of the present disclosure, thephotovoltaic power is generated depending on incident light by thephotoelectric conversion region provided in each pixel and a diffusioncurrent generated by the photovoltaic power is blocked from arriving inthe adjacent pixel by the element isolation region provided between thephotoelectric conversion regions of adjacent pixels in a state ofsubstantially surrounding the photoelectric conversion region.

Advantageous Effects of Invention

According to the first embodiment of the present disclosure, it ispossible to suppress crosstalk between the pixels.

According to the second embodiment of the present disclosure, it ispossible to obtain an image with excellent sensitivity and SIN in lowilluminance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an equivalent circuit diagram for one pixel of a photovoltaictype pixel configuring a logarithmic sensor.

FIG. 2 is a cross-sectional view of a pixel structure corresponding tothe equivalent circuit of FIG. 1.

FIG. 3 is a view illustrating a voltage generated at each temperaturefor the same illuminance.

FIG. 4 is a view illustrating a relationship between irradiation time ofa photovoltaic type pixel and an output voltage.

FIG. 5 is a view illustrating spread of a depletion layer generated in aphoto-sensor in a reverse bias.

FIG. 6 is an equivalent circuit diagram of a photovoltaic type pixelthat is a first embodiment of the present disclosure.

FIG. 7 is a top view of a pixel structure corresponding to thephotovoltaic type pixel of FIG. 6.

FIG. 8 is a cross-sectional view of a pixel structure corresponding tothe photovoltaic type pixel of FIG. 6.

FIG. 9 is a cross-sectional view of a pixel structure corresponding tothe photovoltaic type pixel of FIG. 6.

FIG. 10 is a cross-sectional view illustrating a first configurationexample when the photovoltaic type pixel of FIG. 6 is applied to asurface irradiation type imaging device.

FIG. 11 is a cross-sectional view illustrating a modified example of thefirst configuration example of FIG. 10.

FIG. 12 is a cross-sectional view illustrating a second configurationexample when the photovoltaic type pixel of FIG. 6 is applied to asurface irradiation type imaging device.

FIG. 13 is a cross-sectional view illustrating a third configurationexample when the photovoltaic type pixel of FIG. 6 is applied to asurface irradiation type imaging device.

FIG. 14 is a cross-sectional view illustrating a fourth configurationexample when the photovoltaic type pixel of FIG. 6 is applied to asurface irradiation type imaging device.

FIG. 15 is a cross-sectional view illustrating a fifth configurationexample when the photovoltaic type pixel of FIG. 6 is applied to a backsurface irradiation type imaging device.

FIG. 16 is a cross-sectional view illustrating a first modified exampleof the fifth configuration example illustrated in FIG. 15.

FIG. 17 is a cross-sectional view illustrating a second modified exampleof the fifth configuration example illustrated in FIG. 15.

FIG. 18 is a cross-sectional view illustrating a sixth configurationexample when the photovoltaic type pixel of FIG. 6 is applied to a backsurface irradiation type imaging device.

FIG. 19 is a cross-sectional view illustrating a seventh configurationexample when the photovoltaic type pixel of FIG. 6 is applied to a backsurface irradiation type imaging device.

FIG. 20 is a cross-sectional view illustrating a modified example of theseventh configuration example of FIG. 19.

FIG. 21 is an equivalent circuit diagram of the first to seventhconfiguration examples.

FIG. 22 is a view illustrating a configuration example of an imagingdevice in which the photovoltaic type pixel and the accumulation typepixel are connected to the same vertical signal line.

FIG. 23 is a view illustrating a configuration example of an imagingdevice in which the photovoltaic type pixel and the accumulation typepixel are respectively connected to different vertical signal lines.

FIG. 24 is a view illustrating an example of a drive timing of thephotovoltaic type pixel.

FIG. 25 is a view illustrating an example of a drive timing of theaccumulation type pixel.

FIGS. 26A-26C illustrate examples of three types of an output image ofan imaging device on which the photovoltaic type pixel and theaccumulation type pixel are mounted.

FIG. 27 is a view illustrating an example of a drive timing forobtaining an output image illustrated in FIG. 26C.

FIG. 28 is a view illustrating an example of an arrangement of thephotovoltaic type pixel and the accumulation type pixel.

FIG. 29 is a view illustrating a drive timing corresponding to thearrangement example of FIG. 28.

FIGS. 30A-30F illustrate another example of an arrangement of thephotovoltaic type pixel and the accumulation type pixel.

FIG. 31 is an equivalent circuit diagram of an accumulation type andphotovoltaic type pixel that is a second embodiment of the presentdisclosure.

FIG. 32 is a top view of a pixel structure corresponding to theaccumulation type and photovoltaic type pixel of FIG. 31.

FIG. 33 is a cross-sectional view of the pixel structure correspondingto the accumulation type and photovoltaic type pixel of FIG. 31.

FIG. 34 is a view of a potential distribution of the accumulation typeand photovoltaic type pixel of FIG. 31.

FIG. 35 is a view of the potential distribution of the accumulation typeand photovoltaic type pixel of FIG. 31.

FIG. 36 is a cross-sectional view illustrating an eighth configurationexample when the accumulation type and photovoltaic type pixel of FIG.31 is applied to a surface irradiation type imaging device.

FIG. 37 is a cross-sectional view illustrating a ninth configurationexample when the accumulation type and photovoltaic type pixel of FIG.31 is applied to a back surface irradiation type imaging device.

FIG. 38 is an equivalent circuit diagram illustrating a firstconfiguration example which can be employed in an amplifier of FIG. 31.

FIG. 39 is an equivalent circuit diagram illustrating a secondconfiguration example which can be employed in an amplifier of FIG. 31.

FIG. 40 is another equivalent circuit diagram of the accumulation typeand photovoltaic type pixel that is the second embodiment of thedisclosure.

FIG. 41 is a timing chart when the accumulation type and photovoltaictype pixel is operated as the accumulation type pixel.

FIG. 42 is a timing chart when the accumulation type and photovoltaictype pixel is operated as the photovoltaic type pixel.

FIG. 43 is a timing chart when outputs of the accumulation type pixeland the photovoltaic type pixel are switched for each row inside oneframe.

FIG. 44 is a timing chart when the outputs of the accumulation typepixel and the photovoltaic type pixel are switched for each row insideone frame.

FIG. 45 is a view illustrating an effect obtained when the outputs ofthe accumulation type pixel and the photovoltaic type pixel are switchedfor each row inside one frame.

FIG. 46 is an equivalent circuit diagram for obtaining a higher framerate than that in the drive timing of FIGS. 43 and 44.

FIG. 47 is a timing chart illustrating a higher frame rate.

FIG. 48 is a drive timing chart when employing the circuit configurationof FIG. 46 and simultaneously outputting a pixel signal of theaccumulation type pixel and a pixel signal of the photovoltaic typepixel from different rows.

FIG. 49 is a view illustrating a configuration example of a selectioncircuit for selecting the drive timing of the accumulation type pixeland the drive timing of the photovoltaic type pixel by column unit inthe same row inside one frame.

FIG. 50 is a view illustrating an effect obtained when selecting thedrive timing of the accumulation type pixel and the drive timing of thephotovoltaic type pixel by column unit in the same row inside one frame.

FIGS. 51A-51C illustrate an example of the driving timing whenoutputting both the accumulation type pixel signal and the photovoltaictype pixel signal from all pixels inside one frame.

FIG. 52 is a view illustrating an effect obtained when outputting boththe accumulation type pixel signal and the photovoltaic type pixelsignal from all pixels inside one frame.

FIG. 53 is a view illustrating output voltage characteristics of a PNjunction diode 11.

FIG. 54 is a view illustrating an outline of a calibration method of anoutput value of the photovoltaic type pixel.

DESCRIPTION OF EMBODIMENTS

Hereinafter, best modes (hereinafter, referred to as embodiments) forimplementing the present disclosure are described in detail withreference to the drawings.

1. First Embodiment

A photovoltaic type pixel according to a first embodiment will bedescribed with reference to the drawings. Moreover, the same referencenumerals are appropriately given to common portions in each view.

FIG. 6 illustrates an equivalent circuit of a photovoltaic type pixelaccording to the first embodiment. A photovoltaic type pixel 10 has a PNjunction diode 11, an amplifier 12 and a switch 13. The PN junctiondiode 11 generates photovoltaic power in proportion to a logarithm of aphotocurrent value depending on incident light. The amplifier 12amplifies the generated photovoltaic power and outputs a pixel signalobtained as a result thereof to a subsequent stage. The switch 13generates a diode output voltage when dark by shorting the PN junctiondiode 11.

Moreover, in the equivalent circuit of FIG. 6, the photovoltaic powergenerated in an N-type region is amplified by the amplifier 12 and isused as a signal voltage, but conductive types of the N-type region anda P-type region of FIG. 6 may be switched as displayed in parenthesesand a voltage generated in the P-type region may be used as the signalvoltage. In the following description, unless otherwise specified, acase where a potential of the N-type region is used as the signalvoltage is described as an example.

FIG. 7 illustrates an arrangement view of an upper surface for 2×2pixels of a pixel structure corresponding to the photovoltaic type pixel10 of which the equivalent circuit is illustrated in FIG. 6.

As illustrated in the drawing, the photovoltaic type pixel 10 has aphotoelectric conversion region 21 separated by an element isolationregion 35. The PN junction diode 11 of FIG. 6 is formed in thephotoelectric conversion region 21. A pixel circuit region 22 can beprovided in an appropriate region in the pixel which overlaps with thephotoelectric conversion region 21 or the element isolation region 35and the amplifier 12, the switch 13, and the like besides the PNjunction diode 11 are formed in the pixel circuit region 22.

FIG. 8 illustrates a cross section of the pixel structure in lineVIII-VIII of FIG. 7 and FIG. 9 illustrates a cross section of the pixelstructure in line IX-IX of FIG. 7. As is apparent from the crosssections of FIGS. 8 and 9, isolation between the photoelectricconversion region 21 and the photoelectric conversion region 21 isperformed by the element isolation region 35.

Specifically, as illustrated in FIG. 9, the PN junction diode 11 formedin the photoelectric conversion region 21 is configured of a P-typeregion 31, an N-type region 32, an electrode 33 for ohmic contact withthe P-type region 31, and an electrode 34 for ohmic contact with theN-type region 32.

For example, the P-type region 31 is a Group IV semiconductor such as Siand Ge into which acceptor impurities are introduced, a Group III-Vsemiconductor such as GaAs, InP, and InGaAs, or a Group II-VIsemiconductor selected from Hg, Zn, Cd, Te, and the like.

For example, the N-type region 32 is a Group IV semiconductor such as Siand Ge into which donor impurities are introduced, a Group III-Vsemiconductor such as GaAs, InP, and InGaAs, or a Group II-VIsemiconductor selected from Hg, Zn, Cd, Te, and the like.

The electrodes 33 and 34 are selected depending on a material of theP-type region 31 or the N-type region 32 with which each of theelectrodes 33 and 34 comes into contact. For example, if the P-typeregion 31 and the N-type region 32 are Si, for example, an Al, Ti/Wlaminated film and the like are selected as the electrodes 33 and 34.

The element isolation region 35 is provided to suppress a leakagecurrent between the photoelectric conversion regions 21 (the PN junctiondiodes 11) which are adjacent to each other, and the photoelectricconversion regions 21 which are adjacent to each other. Thus, theelement isolation region 35 is disposed so as to substantially surrounda circumference of the photoelectric conversion region 21 (the PNjunction diode 11).

Moreover, at least one of element isolation regions 35 a and 35 ddisposed above and below the P-type region 31 has optical transparencyin order to cause the incident light to reach the PN junction diode 11.

The element isolation region 35 is configured of one of the followingmaterials or a combination thereof.

Insulating material (SiO₂. SiN, BSG, PSG, SiON, and the like)

Conductive semiconductor (for example, if the PN junction diode 11 isSi, n-Si and the like of a reverse conductive type with respect to theP-type region 31)

Metal (an ohmic electrode and a Schottky electrode for the P-Type region31)

Moreover, the conductive semiconductor as the element isolation region35 may be the same material as the P-type region 31 or the N-type region32 of the PN junction diode 11, and is configured of a different typesemiconductor material and then may form a heterojunction. When it isthe same material, the N-type region is the reverse conductive type withrespect to the P-type region 31. Otherwise, if the photoelectricconversion region and the element isolation region are configured of aGroup III-V semiconductor such as GaAs, boron and the like areion-implanted at a high concentration in the element isolation region 35and it is possible to use a high resistance material by degrading thecrystallinity.

As described above, since electrons diffused from the N-type region 32to the P-type region 31 or electrons generated within the P-type regionare prevented from reaching the adjacent pixel by providing the elementisolation region 35, it is possible to suppress crosstalk to theadjacent pixel.

FIG. 10 is a cross-sectional view of a configuration example(hereinafter, referred to as a first configuration example) in a casewhere the photovoltaic type pixel 10 of the first embodiment is appliedto a surface irradiation type imaging device.

In the first configuration example, SiO₂ is used for the elementisolation region 35 a covering an upper side of the N-type region 32,the conductive semiconductor (n-Si) is used for the element isolationregion 35 b, and an N-type substrate 51 of the conductive semiconductor(n-Si) functions as the element isolation region 35 d covering a lowerside of the P-type region 31.

An NMOS Tr. 36 a of the pixel circuit region 22 is formed in the P-typeregion 31 and a PMOS Tr. 36 b is formed in the element isolation region35 b.

In the first configuration example, the N-type substrate 51 and theelement isolation region 35 b function as a collector of diffusioncurrent from the N-type region 32 to the P-type region 31 and preventflowing of the diffusion current into the adjacent photoelectricconversion region 21, and thereby crosstalk can be suppressed.

A manufacturing method of the first configuration example will bedescribed. First, an N-type epitaxial growth layer 52 of a lowconcentration is laminated on the N-type substrate 51 by an existingmethod. Next, an N-type impurity (for example, phosphorus or arsenic)and a P-type impurity (for example, boron) are ion-implanted in theepitaxial growth layer 52 by an existing method, activation annealing isperformed, and the P-type region and the N-type region (not illustrated)of high concentration are formed respectively in forming regions of theP-type region 31, the N-type region 32, the element isolation region 35b, and the electrodes 33 and 34.

Next, a Si surface of the epitaxial growth layer 52 is thermallyoxidized and then the element isolation region 35 a is formed. Oxidefilms on the P-type region 31 and the N-type region 32 are removed byetching, metal is embedded therein, and then the electrodes 33 and 34are formed. As the metal embedded as the electrodes 33 and 34, forexample, it is possible to use Al, Ti/W laminated film, and the like.

Thereafter, a wiring layer 54 is formed by an existing method andfinally, a condensing layer 55 including an on-chip lens is formed by anexisting method.

FIG. 11 illustrates a modified example of the first configurationexample. That is, as illustrated in FIG. 11, a P-type region 58 isinserted into the element isolation region 35 b and the elementisolation region 35 b, and an element such as an NMOS Tr. 36 c may beformed therein. The P-type region 58 can be formed by introducingimpurities of the P-type region 58 before and after a step ofintroducing acceptor impurities in the P-type region 31.

(Specific Configuration Example of Photovoltaic Type Pixel 10 that isFirst Embodiment)

Next, FIG. 12 is a cross-sectional view of a configuration example(hereinafter, referred to as a second configuration example) in whichthe photovoltaic type pixel 10 of the first embodiment is applied to thesurface irradiation type imaging device.

The second configuration example is configured by laminating anepitaxial growth layer (epitaxial layer) 52, a wiring layer 54, and acondensing layer 55 on an N-type substrate 51 in this order.

In the second configuration example, SiO₂ is used in the elementisolation region 35 a covering the upper side of the N-type region 32, acombination of SiO₂ and the conductive semiconductor (n-Si) is used inthe element isolation region 35 b, and the N-type substrate 51 of theconductive semiconductor functions as the element isolation region 35 dcovering the lower side of the P-type region 31.

A manufacturing method of the second configuration example will bedescribed. First, the N-type epitaxial growth layer 52 of lowconcentration is laminated on the N-type substrate 51 by an existingmethod. Next, an N-type impurity (for example, phosphorus or arsenic)and a P-type impurity (for example, boron) are ion-implanted in theepitaxial growth layer 52, and activation annealing is performed by anexisting method and then the P-type region and the N-type region (notillustrated) of high concentration are formed respectively in formingregions of an N-type region 53, the P-type region 31, the N-type region32, and the electrodes 33 and 34.

Next, an active element such as a MOS Tr. 36 and a passive element suchas MOS capacitor and diffusion layer resistance are formed in the pixelcircuit region 22 by an existing method.

Subsequently, the region forming the element isolation region 35 b ofthe epitaxial growth layer 52 is etched, SiO₂ is embedded therein, andthe element isolation region 35 b is formed. For the etching, it ispossible to use reactive ion etching, a method of anodic oxidation, andthe like. Furthermore, for the embedding of SiO₂ it is possible to usean ALO method, a CVD method, or a combination of CMP technology afterthermally oxidizing Si of the etching surface.

Next, the Si surface of the epitaxial growth layer 52 is thermallyoxidized, the element isolation region 35 a is formed, oxide films onthe P-type region 31 and the N-type region 32 are removed by etching,metal is embedded therein, and then the electrodes 33 and 34 are formed.For the metal that is embedded as the electrodes 33 and 34, for example,it is possible to use Al, an Ti/W laminated film, and the like.

Thereafter, the wiring layer 54 is formed by an existing method and,finally, the condensing layer 55 including an on-chip lens is formed byan existing method.

Moreover, in FIG. 12, distribution of impurities within each of theP-type region 31 and the N-type region 32 is not illustrated, but inorder to increase the sensitivity by widening a width of the depletionlayer formed between both sides, the impurity concentration of aboundary region of both sides is decreased and then an effective p-i-njunction may be formed. In this case, an i layer may be an N-type layerof low concentration or a P-type layer of low concentration. However, inthe configuration example of FIG. 12, the N-type region 32 isillustrated so as to be narrower than the P-type region 31, but when theN-type layer of the low concentration is provided, the N-type region 32is formed so as to be wider than the P-type region 31.

Next, FIG. 13 illustrates a modified example (hereinafter, referred toas a third configuration example) of the second configuration example.In the third configuration example, an element isolation region 35 b isconfigured of a SiO₂ layer 300, a metal layer 301 that is embeddedinside the SiO₂ layer 300 and is separated from a P-type region 31 bythe SiO₂ layer 300, and an N-type region 53. Since the metal layer 301functions as a reflecting mirror with respect to the incident light andlight leakage from the P-type region 31 to the adjacent pixel issuppressed, crosstalk is further suppressed and the sensitivity is alsoimproved.

The third configuration example illustrated in FIG. 13 can bemanufactured by replacing SiO₂ as the material that is embedded after Siof the etching surface is thermally oxidized to a metal such as W or Alin the manufacturing method of the second configuration exampledescribed above.

Next, FIG. 14 is a cross-sectional view of still another configurationexample (hereinafter, referred to as a fourth configuration example) inwhich the photovoltaic type pixel 10 of the first embodiment is appliedto the surface irradiation type imaging device.

In the fourth configuration example, a photovoltaic type pixel 61(corresponding to the photovoltaic type pixel 10) and an accumulationtype pixel 62 are disposed in photoelectric conversion regions adjacentto each other across an element isolation region 35 b.

Moreover, the photovoltaic type pixel 61 of FIG. 14 is the same as thesecond configuration example illustrated in FIG. 12, but may employ thefirst configuration example illustrated in FIG. 10, the modified exampleillustrated in FIG. 11, or the third configuration example illustratedin FIG. 13. On the other hand, for the portion of the accumulation typepixel 62, it is possible to apply the existing configuration asillustrated in FIG. 14.

As illustrated in the view, a PN junction region of the photovoltaictype pixel 61 is substantially surrounded by the element isolationregions 35 a, 35 b, and 35 d, but it is not necessary to surround aportion between the photoelectric conversion region 100 of theaccumulation type pixel 62 and the photoelectric conversion region ofthe adjacent accumulation type pixel 62 by the element isolation region35 b.

For the manufacturing method of the fourth configuration example, themanufacturing process of the first configuration example illustrated inFIG. 1 may be added to the manufacturing method of the existingaccumulation type pixel 62.

Next, FIG. 15 is a cross-sectional view of a configuration example(hereinafter, referred to as a fifth configuration example) in which thephotovoltaic type pixel 10 of the first embodiment is applied to a backsurface irradiation type imaging device.

In the fifth configuration example, a photoelectric conversion region 21and a pixel circuit region 22 are formed on the same substrate (sensorsubstrate 56). Each photoelectric conversion region 21 is substantiallysurrounded by the element isolation regions 35 a, 35 b, and 35 d, andthe element isolation regions 35 a to 35 d are formed of SiO₂.

A manufacturing method of the fifth configuration example will bedescribed. First, a circuit substrate 57 in which a signal processingcircuit and the like are formed and the sensor substrate 56 in which thepixel (photovoltaic type pixel) is formed are attached to each other bya wiring layer 54, and the back surface of the sensor substrate 56 ispolished to a predetermined thickness. Next, a region of the sensorsubstrate 56 that forms the element isolation region 35 b is etched fromthe back surface side and SiO₂ is embedded, and then the elementisolation region 35 b is formed. Furthermore, a SiO₂ oxide film isformed on the back surface of the sensor substrate 56 as the elementisolation region 35 d, and, finally, a condensing layer 55 is laminated.

Moreover, for the polishing of the sensor substrate 56, for example, itis possible to apply a combination of mechanical polishing and a CMPmethod using an existing polishing material. For the etching of thesensor substrate 56, for example, it is possible to apply a reactiveion-etching method. For the embodiment of SiO₂. it is possible to applya chemical vapor deposition method. Moreover, SiO₂ and metal may beembedded similar to the third configuration example illustrated in FIG.13, instead of embedding SiO₂.

In the fifth configuration example illustrated in FIG. 15, as a firstmodified example illustrated in FIG. 16, the element isolation region 35d is configured of a SiO₂ layer 400 and a thin film 401 of HfO laminatedthereon, and hole concentration in the vicinity of the interface of theSiO₂ layer 400 and a P-type region 31 may be increased. Furthermore, asa second modified example illustrated in FIG. 17, acceptor impuritiesare introduced into the P-type region 31 in the vicinity of the SiO₂layer 400 and a P-type region 402 of hole concentration higher than thatof the P-type region 31 may be formed.

Next, FIG. 18 is a cross-sectional view of another configuration example(hereinafter, referred to as a sixth configuration example) of a casewhere the photovoltaic type pixel 10 that is the first embodiment isapplied to the back surface irradiation type imaging device.

In the sixth configuration example, a photoelectric conversion region 21and a pixel circuit region (MOS Tr. 36 and the like) are formed on othersubstrates (a sensor substrate 56 and a circuit substrate 57). Eachphotoelectric conversion region 21 is substantially surrounded by theelement isolation regions 35 a, 35 b, and 35 d, and the elementisolation regions 35 a, 35 b, and 35 d are formed of SiO₂.

An N-type region 32 generating a photovoltaic power is connected to agate of a MOS Tr. 36 a of the circuit substrate 57 by an electrode 34and a wiring 200.

For a manufacturing method of the sixth configuration example, it ispossible to use the manufacturing method of the fifth configurationexample illustrated in FIG. 15.

Moreover, in the sixth configuration example, a case where the sensorsubstrate 56 and the circuit substrate 57 are attached to each other bythe wiring layer 54 is illustrated, but the electrode on the sensorsubstrate 56 and the electrode on the circuit substrate 57 may bebump-connected to each other by using mounting technology and aconfiguration of a so-called hybrid sensor may be employed.

Next, FIG. 19 is a cross-sectional view of still another configurationexample (hereinafter, referred to as a seventh configuration example) inwhich the photovoltaic type pixel 10 of the first embodiment is appliedto the back surface irradiation type imaging device. In the seventhconfiguration example, a photovoltaic type pixel 61 (corresponding tothe photovoltaic type pixel 10) and an accumulation type pixel 62 aredisposed in adjacent photoelectric conversion regions.

Moreover, the photovoltaic type pixel 61 in the seventh configurationexample is the same as the fifth configuration example illustrated inFIG. 15, but may employ the sixth configuration example illustrated inFIG. 18. On the other hand, for the portion of the accumulation typepixel 62, it is possible to apply the existing configuration asillustrated in FIG. 19.

FIG. 20 is a cross-sectional view of still further another configurationexample (hereinafter, referred to as an eighth configuration example) inwhich the photovoltaic type pixel 10 that is the first embodiment isapplied to the back surface irradiation type imaging device. In theeighth configuration example, similar to the seventh configurationexample, a photovoltaic type pixel 61 (corresponding to the photovoltaictype pixel 10) and an accumulation type pixel 62 are disposed inadjacent photoelectric conversion regions. Furthermore, similar to thesixth configuration example, a photoelectric conversion region 21 and apixel circuit region (MOS Tr. 36 and the like) are formed on othersubstrates (a sensor substrate 56 and a circuit substrate 57) and anN-type region 32 generating the photovoltaic power and a FD of theaccumulation type pixel 62 are respectively connected to a gate of a MOSTr. 36 a of a circuit substrate 57 by an electrode 34 and a wiring 200.

Each configuration example of the photovoltaic type pixel 10 that is thefirst embodiment described above can be configured of a known circuit(for example, a circuit of FIG. 1 of PTL 1, circuits of FIGS. 3a and 3bof PTL 2, and the like). Of course, as illustrated in FIG. 21, apositive potential generated in a P-type region of a PN junction diodeis taken out as a signal and may be deformed so as to be applied to agate of a depletion type MOSFET configuring an amplifier 12.

FIG. 22 illustrates a configuration example of an imaging device inwhich a photovoltaic type pixel 61 and an accumulation type pixel 62 areconnected to the same vertical signal line. In the configurationexample, it is possible to mix both by disposing both in the sameimaging device without increasing the number of the vertical signallines and without sacrificing an aperture ratio in the surfaceirradiation type.

FIG. 23 illustrates a configuration example of an imaging device inwhich a photovoltaic type pixel 61 and an accumulation type pixel 62 arerespectively connected to other vertical signal lines. In theconfiguration, since pixel signals of the photovoltaic type pixel 61 andthe accumulation type pixel 62 can be output simultaneously to a columnsignal processing section, it is possible to obtain a higher frame rate.Furthermore, since a column signal processing circuit can be optimallydesigned depending on each output voltage range, it is possible toreduce circuit noise with respect to each pixel signal and to obtaingood image quality.

Next, FIG. 24 illustrates an example of a drive timing of thephotovoltaic type pixel 61.

When an exposure period is started, a Reset 73 in the exposure period isturned off. As a result, the PN junction diode 11 is opened, a generatedphotocurrent is cancelled by a forward current of the PN junction diode11, and a forward voltage is generated so that a net DC current is zero.

When an exposure period ends, a control signal for a reading row SEL 75is turned on and a forward voltage VSG 1 of a PN junction diode. 11 thatis amplified by the amplifier 12 is output to the vertical signal line.The pixel output that is output is AD-converted and becomes a digitaloutput value of a VSG 1.

Next, a Reset 73 is turned on and an output voltage (voltage when dark)VDK 2 when the PN junction diode 11 is shorted is output to the verticalsignal line. The pixel output that is output is AD-converted and becomesa digital output value of the VDK 2. A value obtained by subtracting thedigital output value of the VSG 1 and the VDK 2 is a digital outputvalue of the pixel.

Moreover, as the voltage when dark, the output voltage VDK 1 before theexposure period may be read. It is possible to perform two readingmethods of step 1 and step 2 in the photovoltaic type pixel 61 byreading the VDK 1 before the exposure period or reading the VDK 2 afterthe exposure period. In the following description, step 2 is employed(step in which the signal voltage VSG 1 and the voltage VDK 2 when darkare sequentially read after the exposure period).

It is possible to employ the drive timing of the accumulation type pixelthat is known in the related art as illustrated in FIG. 25 in the drivetiming of the accumulation type pixel 62 disposed together with thephotovoltaic type pixel 61 on the same imaging device.

Next, FIGS. 26A to 26C illustrate examples of three types of outputimage from the imaging device on which the photovoltaic type pixel 61and the accumulation type pixel 62 are mounted.

In FIG. 26A, an output image is arranged in time series in a case whereonly one of the photovoltaic type pixel 61 and the accumulation typepixel 62 over a plurality of frames (here, only each three frames areillustrated before and after switching the output image from a linearimage to a logarithmic image) is read. Such an image output order can beobtained by switching the drive timing of FIGS. 24 and 25 for aplurality of frames. Moreover, here, an image configured of thephotovoltaic type pixel output is referred to as the logarithmic imageand an image configured of the accumulation type pixel output isreferred to as the linear image.

In FIG. 26B, a reading pixel and an output image are arranged in timeseries in a case where the photovoltaic type pixel 61 and theaccumulation type pixel 62 are alternately read and the logarithmicimage and the linear image are synthesized and output for one frame.Such an image output order can be obtained by switching the drivetimings of FIGS. 24 and 25 for one frame and synthesizing thelogarithmic image and the linear image by a known method. It is possibleto obtain good low illuminance sensitivity and SIN by using the signalof the accumulation type pixel in a low luminance portion in the imageand to obtain a tone and color reproduction with a higher luminance byusing the signal of the logarithmic type pixel in a high luminanceportion exceeding a dynamic range of the accumulation pixel.

In FIG. 26C, a reading pixel and an output image are arranged in timeseries in a case where both the photovoltaic type pixel 61 and theaccumulation type pixel 62 are read and the logarithmic image and thelinear image are synthesized and output for one frame. In this case,since exposure times of the photovoltaic type pixel 61 and theaccumulation type pixel 62 overlap and imaging timings of the linearimage and the logarithmic image approach each other, it is possible tosuppress generation of artifacts caused by imaging time difference in asynthesized image. Furthermore, it is possible to output the synthesizedimage at a frame rate higher than that of a case of FIG. 26B.

FIG. 27 illustrates an example of a drive timing of the photovoltaictype pixel 61 and the accumulation type pixel 62 in one frame period forobtaining the output image illustrated in FIG. 26C.

In the accumulation type pixel 62, in the period A, a shutter row SEL75, a RST 74, and a TG 71 are turned on and charges of the chargeaccumulation region (PD) and a floating diffusion layer (FD) are sweptso that an electronic shutter is turned off. In the next period B, thesignal charge is accumulated in the PD. Furthermore, in a period C, areading row SEL 75 and the RST 74 are turned on and the charge insidethe FD is swept again and in a period E, a voltage (P phase voltage) VDKwhen dark is read. Furthermore, in a period G, the TG 71 is turned onand the charge accumulated in the PD is transferred to the FD, thesignal voltage is generated in the FD, and in a period I, a signalvoltage VSG amplified by the amplifier 12 is read.

Meanwhile, in the photovoltaic type pixel 61 formed in the same row asthe accumulation type pixel 62, exposure is started from a period K ofthe previous frame and the photovoltaic power is generated in the PNjunction diode 11. Next, in the period C, the reading row SEL 75 isturned on and the photovoltaic power generated in the PN junction diode11 is amplified by the amplifier 12 and then is output to the verticalsignal line, and is read as the signal voltage VSG 1. Substantially, inperiods G, H, I, and J, the RST 73 is turned on, the PN junction diode11 is shorted, and in the period I, the voltage VDK 2 when dark is read.

Next, FIG. 28 illustrates an example of an arrangement of thephotovoltaic type pixel 61 and the accumulation type pixel 62 for 2×2pixels in the imaging device. Moreover, in FIG. 28, R (Red), G (Green),and B (Blue) respectively illustrate a color of a color filter coveringeach pixel, Log illustrates the photovoltaic type pixel 61, and Linillustrates the accumulation type pixel 62.

FIG. 29 illustrates drive timings of the accumulation type pixel 62 of a(2n−1)-th column and a (2m−1)-th row, and the photovoltaic type pixel 61of a (2n−1)-th column and a 2m-th row of FIG. 28.

In the (2n−1)-th column, the photovoltaic type pixel 61 and theaccumulation type pixel 62 are alternately read for one row readingperiod (horizontal synchronization period and 1H period). Meanwhile, inthe adjacent a 2n-th row (not illustrated), in all reading periods, theaccumulation type pixel 62 is read. That is, the photovoltaic type pixel61 and the accumulation type pixel 62 can be read simultaneously withinone frame.

Since the photovoltaic type pixel 61 and the accumulation type pixel 62are read at the same time when the common exposure period B ends, anexposure timing difference does not occur between the photovoltaic typepixel 61 and the accumulation type pixel 62 of the same row. Thus, noimage shift occurs between the logarithmic image and the linear image.As a result, when synthesizing both, occurrence of artifacts due to theimage shift is suppressed and a synthesized image of good image qualitycan be obtained.

FIGS. 30A to 30F illustrate another example of the arrangement of thephotovoltaic type pixel 61 and the accumulation type pixel 62 in theimaging device. Moreover, in FIGS. 30A to 30F, R, G, B, and W (colorlessor complementary color) respectively illustrate color of the colorfilter covering each pixel, Log illustrates the photovoltaic type pixel61, and Lin illustrates the accumulation type pixel 62.

FIG. 30A is an arrangement example in which one pixel is thephotovoltaic type pixel 61 of G and another three pixels are theaccumulation type pixels 62 in four pixels configuring a Bayer array.

FIG. 30B is an arrangement example in which the photovoltaic type pixel61 of G in the arrangement illustrated in FIG. 30A is replaced by thephotovoltaic type pixel 61 of W.

FIG. 30C is an arrangement example in which one pixel is theaccumulation type pixel 62 of G and another three pixels are thephotovoltaic type pixels 61 in four pixels configuring the Bayer array.

FIG. 30D is an arrangement example in which the accumulation type pixel62 of G in the arrangement illustrated in FIG. 30C is replaced by theaccumulation type pixel 62 of W.

FIG. 30E is an arrangement example in which all four pixels configuringthe Bayer array are the photovoltaic type pixels 61.

FIG. 30F is an arrangement example in which one pixel of twophotovoltaic type pixels 61 of G in the arrangement illustrated in FIG.30E is replaced by the photovoltaic type pixel 61 of W.

As the arrangement examples illustrated in FIGS. 30A and 30C, it ispossible to calibrate the pixel output value of the photovoltaic typepixel 61 with the output value of the accumulation type pixel 62 that isnot saturated and to compensate for temperature characteristic variationof the photovoltaic type pixel 61 or characteristic variation for eachpixel by closely disposing the accumulation type pixel 62 and thephotovoltaic type pixel 61 of the same color. Thus, in the synthesizedimage of the linear image and the logarithmic image, it is possible toobtain a smooth tone or gradation in the boundary of the linear imageand the logarithmic image.

Moreover, for example, in the arrangement example illustrated in FIG.30B, even if output of one of three accumulation type pixels 62 of R, G,and B is saturated, it is possible to obtain a certain degree of colorreproducibility and tone by using the output of remaining accumulationtype pixels 62 and the output of the photovoltaic type pixel 61 that arenot saturated.

As the arrangement examples illustrated in FIGS. 30B, 30D, and 30F, itis possible to increase the sensitivity of the photovoltaic type pixel61 or the accumulation type pixel 62, and to obtain the logarithmicimage in a lower illuminance and the linear image having good SIN byproviding the pixel of W.

2. Second Embodiment

Next, a photovoltaic type pixel (hereinafter, referred to as anaccumulation type and photovoltaic type pixel) that can also be operatedas an accumulation type pixel, that is a second embodiment will bedescribed.

FIG. 31 illustrates an equivalent circuit of the accumulation type andphotovoltaic type pixel according to the second embodiment. Anaccumulation type and photovoltaic type pixel 70 is configured of a PNjunction diode 11, an amplifier 12, a TG 71, an FD 72, an RST 73, an RST74, and an Sel 75.

The PN junction diode 11 is configured of a P-type region 31 and anN-type region (charge accumulation region) 32 (all in FIG. 19), andperforms the photoelectric conversion depending on the incident light,and accumulates the signal charges generated as a result thereof orgenerates the photovoltaic power.

The TG 71 transfers the generated signal charges to the FD 72.Furthermore, the TG 71 transfers the generated photovoltaic power to theFD 72 by shorting the N-type region 32 in the FD 72 by a channel formedunder the TG 71.

The FD 72 is the N-type region and converts the signal charges into thesignal voltage. The RST 73 resets the FD 72 to a GND potential. The RST74 resets the FD 72 to a VDD potential. The amplifier 12 amplifies thepotential of the FD 72. The Sel 75 transfers an output signal of theamplifier 12 to a vertical signal line VSL.

FIG. 32 illustrates an arrangement view of an upper surface of 2×2pixels of a pixel structure corresponding to the accumulation type andphotovoltaic type pixel 70 of which the equivalent circuit isillustrated in FIG. 31. As illustrated in the drawing, the accumulationtype and photovoltaic type pixel 70 has a photoelectric conversionregion 21 which is substantially isolated by an element isolation region35. The PN junction diode 11, the TG 71, and the FD 72 of FIG. 31 areformed in the photoelectric conversion region 21. The amplifier 12, theRST 73, the RST 74, the Sel 75, and the like are formed in the pixelcircuit region 22 provided in an appropriate region overlapping with thephotoelectric conversion region 21 or the element isolation region 35.

FIG. 33 illustrates a cross section of the pixel structure in lineXXXIII-XXXIII of FIG. 32. As illustrated in the drawing, isolationbetween the photoelectric conversion region 21 and the photoelectricconversion region 21 is performed by the element isolation region 35.

As is apparent by comparing FIG. 32 and the cross-sectional views (FIGS.8 and 9) of the photovoltaic type pixel 10 of the first embodiment, theaccumulation type and photovoltaic type pixel 70 is structurallydifferent from the photovoltaic type pixel 10 in that the FD 72 isprovided inside thereof surrounded by the element isolation regions 35a, 35 b, 35 c, and 35 d, the electrode (ohmic electrode) 34 is connectedto the FD 72, and the TG 71 is provided for controlling the potentialbarrier between the FD 72 and the N-type region (charge accumulationregion) 32.

Next, FIGS. 34 and 35 are potential distribution views of theaccumulation type and photovoltaic type pixel 70, FIG. 34 corresponds toline A of FIG. 33 and FIG. 35 corresponds to line B of FIG. 33.Moreover, in FIGS. 34 and 35, a case where the element isolation region35 a is SiO₂, and 35 b and 35 d are the N-type regions is illustrated.As illustrated in the drawing, it is preferable that a height of thepotential barrier of the circumference of the N-type region (chargeaccumulation region) 32 of the accumulation type and photovoltaic typepixel 70 is substantially uniform in all directions and is distributedto a height of the potential of a P-type neutral region.

It is possible to operate the accumulation type and photovoltaic typepixel 70 illustrated in FIG. 31 as the accumulation type pixel or thephotovoltaic type pixel due to this potential distribution.

(Specific Configuration Example of Accumulation Type and PhotovoltaicType Pixel 70 of Second Embodiment)

FIG. 36 is a cross-sectional view of a configuration example(hereinafter, referred to as an eighth configuration example) when theaccumulation type and photovoltaic type pixel 70 of the secondembodiment is applied to the surface irradiation type imaging device.

Moreover, element isolation regions 35 a to 35 d of the eighthconfiguration example use the same material as that of the elementisolation regions 35 a to 35 d of the second configuration exampleillustrated in FIG. 12, but may be the same configuration as the elementisolation regions 35 a to 35 d of the first configuration exampleillustrated in FIG. 11 or the third configuration example illustrated inFIG. 13.

A manufacturing method of the eighth configuration example will bedescribed. It is possible to manufacture the eighth configurationexample by slightly modifying the manufacturing method of the surfaceirradiation type and accumulation type pixel (for example, theaccumulation type pixel 62 in the fourth configuration exampleillustrated in FIG. 14) of the related art as described below and byadding a forming process of the element isolation regions 35 a to 35 d.

An acceptor impurity is introduced into a region (a region between theN-type substrate 51 and the N-type region 32 in the P-type region 31)forming the overflow barrier in the accumulation type pixel of therelated art so as to form the P-type neutral region. Therefore, whenoperating the eighth configuration example as the photovoltaic typepixel, it is possible to generate the same photovoltaic power as that ofthe photovoltaic type pixel of the first embodiment.

The acceptor impurity is introduced into the P-type region 31 or a filmthat generates negative fixed charges is embedded inside SiO₂ of theelement isolation region 35 b so that a hole concentration in thevicinity of the interface of the P-type region 31 and the elementisolation region 35 b is set so as to have a predetermined concentrationor more. As the film generating the negative fixed charges, for example,it is possible to use a hafnium oxide film and as a film depositionmethod, it is possible to use a chemical vapor deposition method, asputtering method, an atomic layer deposition method, and the like.Therefore, when operating the eighth configuration example as theaccumulation type pixel, it is possible to reduce the dark current tothe same level as that of the accumulation type pixel of the relatedart.

Next, FIG. 37 is a cross-sectional view of a configuration example(hereinafter, referred to as a ninth configuration example) when theaccumulation type and photovoltaic type pixel 70 of the secondembodiment is applied to the back surface irradiation type imagingdevice.

Moreover, element isolation regions 35 a to 35 d of the ninthconfiguration example use the same material as that of the elementisolation regions 35 a to 35 d of the fifth configuration exampleillustrated in FIG. 15, but may be the same configuration as the firstor second modified example illustrated in FIG. 16 or 17. Furthermore,the element isolation regions 35 a to 35 d may be the same configurationas the sixth configuration example illustrated in FIG. 18 or the seventhconfiguration example illustrated in FIG. 19. Otherwise, similar to thethird configuration example illustrated in FIG. 13, the elementisolation region 35 b may be also configured of SiO₂ and metal.

A manufacturing method of the ninth configuration example will bedescribed. It is possible to manufacture the ninth configuration exampleby slightly modifying the manufacturing method of the back surfaceirradiation type and accumulation type pixel of the related art asdescribed below and by adding a forming process of the element isolationregions 35 a to 35 d. That is, an acceptor impurity is introduced intothe P-type region 31 or a film that generates negative fixed charges isembedded inside SiO₂ of the element isolation region 35 b so that thehole concentration in the vicinity of the interface of the P-type region31 and the element isolation region 35 b is set so as to have apredetermined concentration or more. As the film generating the negativefixed charges, for example, it is possible to use a hafnium oxide filmand as a film deposition method, it is possible to use a chemical vapordeposition method, a sputtering method, an atomic layer depositionmethod and the like. Therefore, when operating the ninth configurationexample as the accumulation type pixel, it is possible to reduce thedark current to the same level as that of the accumulation type pixel ofthe related art.

(Configuration Example of Amplifier 12 of Equivalent Circuit ofAccumulation Type and Photovoltaic Type Pixel 70)

Next, FIG. 38 illustrates a first configuration example capable ofemploying the amplifier 12 in the equivalent circuit of the accumulationtype and photovoltaic type pixel 70 illustrated in FIG. 31.

The first configuration example is a configuration example of theaccumulation type and photovoltaic type pixel 70 when the amplifier 12is configured as a source-follower type amplifier using a depletion-typeMOSFET. It is possible to amplify a negative signal voltage whenoperating the same pixel as the photovoltaic type pixel in addition tothe positive signal voltage when operating as the accumulation typepixel by using the depletion-type MOSFET.

FIG. 39 illustrates a second configuration example capable of employingthe amplifier 12 in the equivalent circuit of the accumulation type andphotovoltaic type pixel 70 illustrated in FIG. 31. The secondconfiguration example is a configuration example of the accumulationtype and photovoltaic type pixel 70 in a case where a charge MOSFET (notillustrated) operated as a constant current source of a source followertype amplifier of FIG. 38 is disposed on the vertical signal line. It ispossible to obtain an aperture ratio or a saturation charge amountequivalent to the accumulation type pixel of the related art bydisposing the charge MOSFET outside the pixel.

FIG. 40 illustrates an equivalent circuit of the accumulation type andphotovoltaic type pixel 70 that can be replaced with the equivalentcircuit of FIG. 31. A Reset 73 of the equivalent circuit is turned on ina period in which one of the Reset 73 and a Reset 74 of FIG. 31 isturned on. Furthermore, in the equivalent circuit of FIG. 40, a GNDpotential is applied to a VRESET in a period in which the Reset 73 isturned on in the equivalent circuit of FIG. 31 and a VDD potential isapplied to the VRESET in a period in which the Reset 74 is turned on.Thus, a reset period of a FD can be determined simply by a signalapplied to the Reset 73 regardless of whether the accumulation type andphotovoltaic type pixel 70 is operated in either the photovoltaic typeor the accumulation type. Whether the FD potential is set to thepotential of either VDD or the GND can be determined by a voltageapplied to the VRESET depending on whether the accumulation type andphotovoltaic type pixel 70 is operated as either the photovoltaic typeor the accumulation type.

Next, FIG. 41 illustrates an example of a drive timing when theaccumulation type and photovoltaic type pixel 70 is operated as theaccumulation type pixel.

The drive timing is the same as the drive timing of the accumulationtype pixel of the related art illustrated in FIG. 25 except that theReset 73 is typically fixed to the GND. That is, the accumulation typeand photovoltaic type pixel 70 can be driven similar to the accumulationtype pixel of the related art if the Reset 73 is typically fixed to theGND.

FIG. 42 illustrates an example of a drive timing when the accumulationtype and photovoltaic type pixel 70 is operated as the photovoltaic typepixel.

The drive timing is the same as the drive timing of the photovoltaictype pixel 61 illustrated in FIG. 24 except that the Reset 74 istypically fixed to the GND. That is, the accumulation type andphotovoltaic type pixel 70 can be driven similar to the photovoltaictype pixel 61 if the Reset 74 is typically fixed to the GND.

Thus, if the drive timing illustrated in FIG. 41 and the drive timingillustrated in FIG. 42 are appropriately selected for each frame, it ispossible to realize the image output sequence illustrated in FIG. 26A or26B.

However, in the accumulation type and photovoltaic type pixel 70, sinceall pixels can be configured of the logarithmic image and the linearimage, it is possible to obtain the image of resolution in any imagehigher than the imaging device to which the first embodiment is applied.

Furthermore, if characteristics in which all pixels are operated as boththe accumulation type and the photovoltaic type are utilized, it ispossible to switch the pixel output of the accumulation type and thephotovoltaic type by row unit within one frame.

FIGS. 43 and 44 illustrate an example of a drive timing that is switchedwhenever the pixel output of the accumulation type and the photovoltaictype is switched for each row within one frame. That is, the drivetiming in which the accumulation type and photovoltaic type pixel 70 isoperated as the accumulation type pixel illustrated in FIG. 41 for afirst to (i−1)-th rows is employed and the drive timing in which theaccumulation type and photovoltaic type pixel 70 is operated as thephotovoltaic type pixel illustrated in FIG. 42 for an i-th to V-th rowsis employed.

It is possible to obtain effects illustrated in FIG. 45 by driving theaccumulation type and photovoltaic type pixel 70 as illustrated in FIGS.43 and 44. FIG. 45 illustrates effects that are obtained when an objectof high luminance suddenly appears in a scene during video recording inthe linear image.

In a region in which the object of high luminance appears, an output ofa part of the accumulation type pixel is saturated. In this case, in theimaging device, the pixel in which the accumulation type output issaturated is detected by a control circuit (not illustrated) and thedrive timing of a certain row of the pixels is selectively changed fromthe accumulation type to the photovoltaic type in the next frame. Thus,in the next frame, the row in which the object of high luminance iscaptured is imaged by the pixel that is driven by the photovoltaic type,but the row in which the object of high luminance is not captured isimaged by the accumulation type timing. In the region of the lowluminance, the SIN is good and it is possible to obtain a synthesizedimage of high resolution having good tone and color reproducibility evenin the object of high luminance by synthesizing the logarithmic imageand the linear image imaged as described above.

Next, FIG. 46 illustrates an example of an equivalent circuit for onepixel for obtaining a higher frame rate in the drive timing illustratedin FIGS. 43 and 44.

As illustrated in the drawing, each pixel is connected to two verticalsignal lines VSL 1 and VSL 2, and whether the pixel output is performedin either vertical signal lines VSL 1 or VSL 2 can be selected byselection transistors 75 and 75 a. Two vertical signal lines VSL 1 andVSL 2 are connected to column signal processing sections 1 and 2 thatare independent from each other, and the column signal processingsections 1 and 2 can perform column signal processes such as ADconversion simultaneously and in parallel to the pixel output from thevertical signal lines VSL 1 and VSL 2.

It is possible to use both two vertical signal lines VSL 1 and VSL 2 inthe row in which the accumulation type and photovoltaic type pixel 70 isoperated as the accumulation type and in the row in which theaccumulation type and photovoltaic type pixel 70 is operated as thephotovoltaic type by employing the circuit configuration illustrated inFIG. 46. In this case, it is possible to simultaneously output the pixelsignal in the row in which the accumulation type and photovoltaic typepixel 70 is driven as the accumulation type and in the row in which theaccumulation type and photovoltaic type pixel 70 as driven in thephotovoltaic type. As a result, as the timing chart illustrated in FIG.47, since the reading of the accumulation type can be started before thereading of the photovoltaic type ends (period A in the drawing), it ispossible to increase the frame rate.

Next, FIG. 48 illustrates an example of a drive timing when the circuitconfiguration illustrated in FIG. 46 is employed and the pixel signal ofthe accumulation type and the pixel signal of the photovoltaic type aresimultaneously output from different rows.

In the drawing, a P phase voltage of the accumulation type and a signalvoltage of the photovoltaic type are simultaneously read and a D phasevoltage of the accumulation type and a voltage when dark of thephotovoltaic type are simultaneously read. Since the accumulation typepixel signal of a certain row and the photovoltaic type pixel signal ofanother row can be simultaneously AD-converted by being synchronized asdescribed above, it is possible to obtain a higher frame rate. Moreover,in an exposure period of the photovoltaic type drive, a voltage of theTG 71 may be set to potentials (L and M in the drawing) that are lowerthan the VDD. Thus, it is possible to reduce an effective junctioncapacitance of a PN junction diode 11 and to stabilize the photovoltaicpower generated in the PN junction diode 11 in a shorter time.

Next, FIG. 49 illustrates an example of a selection circuit forselecting the drive timing of the accumulation type and the drive timingof the photovoltaic type in the same row within one frame by columnunit.

Moreover, in the drawing, the TG 71 represents a transfer gate signalfor the photovoltaic type timing. A TG 71 a represents a transfer gatesignal for the accumulation type timing. The Resets 73 and 74 representthe reset signals for the photovoltaic type timing. Resets 73 a and 74 arepresent reset signals for the accumulation type timing. A ROWSEL 76 isa signal that is turned on during a row selection period.

A mode selection line 500 is a signal line that transmits timingselection signals (the accumulation type is selected for OV and thephotovoltaic type is selected for the VDD) of the photovoltaic type andthe accumulation type and is provided for each pixel column or for apredetermined column interval. A signal selection circuit 501 isprovided for selecting the signal transmitted to the transfer gate 71and the reset gates 73 and 74 by the signal voltage of the modeselection line. A transmission latch circuit has terminals D, E, and Q,and an input voltage of the terminal D is output to the terminal Q whenthe ROWSEL 76 is turned on and next, when the ROWSEL 76 is turned off,the voltage of the terminal Q when being turned off is held until thenext time it is turned on.

In the selection circuit illustrated in the drawing, when the ROWSEL 76of the reading row is turned on, the drive signal of the accumulationtype or the photovoltaic type is selected by a MOS switch depending onthe signal voltage of the mode selection line 500 and the drive signalis transmitted to the transfer gate 71 and the reset gates 73 and 74though the transmission latch circuit. That is, whether a certain pixelis driven as the accumulation type or is driven as the photovoltaic typeis determined by the signal voltage of the mode selection line 500.Thus, it is possible to optionally select the drive timing of each pixelof a selected row for each column by changing the signal voltage of themode selection line 500 for each column.

When the ROWSEL 76 is turned off, since the output voltage of thetransmission latch circuit is held, the signal voltage of theaccumulation type or the photovoltaic type is held until the row isselected the next time. Thus, each pixel is driven at one of timings ofthe accumulation type or the photovoltaic type though one frame period.

Moreover, the selection circuit illustrated in FIG. 49 may be providedfor each pixel or, for example, may be provided for each repetitionperiod of the Bayer array. Otherwise, the selection circuit may beprovided for each greater region. In either case, it is preferable thatthe pixel structure is the back surface irradiation type and theselection circuit is disposed on a circuit substrate 57 so that theselection circuit does not limit the aperture ratio of the pixel or theaccumulation charge amount.

Effects illustrated in FIG. 50 can be obtained by providing theselection circuit of FIG. 49. FIG. 50 illustrates effects that areobtained when the object of high luminance suddenly appears in the sceneduring video recording in the linear image.

In a region in which the object of high luminance is captured, an outputof a part of the accumulation type pixel is saturated. In the imagingdevice, the pixel in which the output is saturated is detected by acontrol circuit (not illustrated) and the drive timing of a region ofthe pixels in which the output is saturated is selectively changed tothe photovoltaic type in the next frame. In the next frame, since theselection signal of the photovoltaic type is output to the modeselection line 500 of the region in which the object of high luminanceis captured, the object of the high luminance is imaged in the drivetiming of the photovoltaic type and the other region is imaged in thedrive timing of the accumulation type.

In a region other than the region in which the object of the highluminance is captured, the SIN is good and it is possible to obtain asynthesized image of high resolution having good tone or colorreproducibility even in the object of the high luminance by synthesizingand outputting the logarithmic image and the linear image imaged asdescribed above.

Next, FIGS. 51A to 51C illustrate an example of the drive timing whenboth of the accumulation type pixel signal and the photovoltaic typepixel signal are output from all pixels within one frame.

As illustrated in the drawing, each pixel is driven in the accumulationtype timing illustrated in FIG. 48 immediately after the photovoltaictype pixel signal is output in the drive timing of the photovoltaic typeillustrated in-FIG. 48, and then the accumulation type pixel signal isoutput. As a result, it is possible to obtain both the logarithmic imageand the linear image by all pixels configuring one frame.

Furthermore, in the case of FIGS. 51A to 51C, since the exposure periodof the photovoltaic type and the accumulation type are continuous, shiftof the exposure timing of both is small. As a result, since image shiftof the logarithmic image and the linear image is reduced, artifactgeneration is suppressed in the synthesized image of both.

Furthermore, it is possible to obtain the effects illustrated in FIG. 52by using the drive timing of FIGS. 51A to 51 C. FIG. 52 illustrateseffects that are obtained when the object of high luminance suddenlyappears in the scene during video recording in the linear image.

In a region in which the object of high luminance is captured, an outputof a part of the accumulation type is saturated. However, since allpixels within one frame output the pixel signal of both the photovoltaictype and the accumulation type, it is possible to synthesize thelogarithmic image and the linear image by referring to the photovoltaictype output in the pixel in which an accumulation type output issaturated by storing the output to a line buffer or a frame buffer. As aresult, as illustrated in FIG. 52, in a region other than the region inwhich the object of the high luminance is captured from the first framein which the object of the high luminance appears, the S/N is good andit is possible to obtain a synthesized image of high resolution havinggood tone or color reproducibility even in the object of the highluminance.

Moreover, the circuit configuration illustrated in FIG. 46 may beoperated in the drive timing illustrated in FIG. 51A and, in this case,it is possible to simultaneously output the photovoltaic type pixelsignal and the accumulation type pixel signal respectively fromdifferent rows so as to be performed in a period a of FIG. 51 C. Thus,it is possible to increase the frame rate in the drive timing of FIGS.51 A to 51C.

<Output Voltage Characteristics of FD 37>

Next, FIG. 53 illustrates simulation results of the output voltage ofthe FD 72 corresponding to the irradiation light in a state where the TG71 is turned on in the eighth configuration example illustrated in FIG.36. As illustrated in the drawing, it can be understood that the outputvoltage of the FD 72 logarithmically increases with respect to theilluminance. That is, it can be understood that the eighth configurationexample is also operated as the photovoltaic type pixel.

<Calibration of Output Value of Photovoltaic Type Pixel>

FIG. 54 illustrates an outline of a calibration method of an outputvalue of the photovoltaic type pixel by using the output value of theaccumulation type pixel of the same pixel or the adjacent pixel.

Moreover, in the drawing, Is and Vs represent an exposure amount and apixel output value when the pixel is driven in the accumulation typetiming and the accumulation charge amount is saturated. A graph G1schematically represents a relationship between the output value of theaccumulation type and the exposure amount when any pixel is driven inthe accumulation type timing or a relationship between the pixel outputvalue and the exposure amount expected if it is assumed that the pixelis driven in the accumulation type timing. A graph G2 schematicallyrepresents a relationship between the output value of the photovoltaictype and the exposure amount before calibration when the pixel of thegraph G1 is driven in the photovoltaic type timing. A graph G3schematically represents a relationship between the pixel output valueand the exposure amount that is obtained by converting the pixel outputvalue of the graph G2 from a logarithmic value to a linear value. Agraph G4 schematically represents a relationship between the outputvalue of the photovoltaic type and the exposure amount after calibrationof the output value of the photovoltaic type of the graph G2 using acomparison result of the graph G3 and the graph G 1.

Here, “the output value of the accumulation type (or, its expectedvalue) of any pixel” indicates an average value (or, its expected value)of the accumulation type output of a plurality of pixels of the samecolor configuring an imaging device, or an output value (or, itsexpected value) of the accumulation type of an individual pixel.Similarly, “the output value of the photovoltaic type of any pixel”indicates an average value of the photovoltaic type output of aplurality of pixels of the same color configuring an imaging device, oran output value of the photovoltaic type of an individual pixel.

First, an accumulation type pixel output V1 and a photovoltaic typepixel output V2 are acquired by an exposure amount 1 _(|) in which asignal amount when driving as the accumulation type is not saturated.Next, a value of the photovoltaic type pixel output V2 is converted fromthe logarithmic value to the linear value and an output value V3 of thephotovoltaic type after linear conversion is obtained. A calibrationparameter of the output value of the photovoltaic type is calculatedsuch that the output value V3 of the photovoltaic type coincides withthe accumulation type pixel output VI. Thereafter, it is possible toobtain the photovoltaic type output smoothly leading to the accumulationtype pixel output by calibrating the output value of the photovoltaictype using the calibration parameter.

Here, the accumulation type pixel output V1 can be the signal amountwhen any pixel is driven in the accumulation type timing and thephotovoltaic type pixel output V2 can be the signal amount when the samepixel is driven in the photovoltaic type timing.

Otherwise, the photovoltaic type pixel output V2 can be the signalamount when any pixel is driven in the photovoltaic type tinling and theaccumulation type pixel output VI can be a signal amount predicted valuewhen the pixel is driven in the accumulation type timing. Here, thesignal amount predicted value can be obtained from the output value ofthe accumulation type of near one or a plurality of pixels of the samecolor using a method such as interpolation.

Moreover, the calibration parameter described above may be determinedfor each individual sensor, may be determined for each predeterminedpixel region, or may be determined for an individual pixel. Furthermore,the calibration parameter may be calculated in an inspection step beforeshipment of the imaging device or may be calculated from an image imagedafter the shipment of the imaging device.

Thus, the calibration parameter obtained as described above is recordedin the substrate 54 in which the pixel is formed, the circuit substrate57, or a storage element formed in another substrate (not illustrated)mounted on the same package as the substrate 54, and then thecalibration parameter can be referred to when synthesizing thelogarithmic image and the linear image.

Otherwise, the calibration parameter is transferred and stored in animage processing device (not illustrated) outside of the imaging deviceand then the calibration parameter can be referred to when synthesizingthe logarithmic image and the linear image by the image processingdevice.

As described above, it is possible to obtain the output value that iscontinuous to the output value of the accumulation type pixel bycalibrating the output value of the photovoltaic type even when theoutput value of the photovoltaic type pixel is changed by thetemperature. Thus, it is possible to suppress the luminance or colorlevel difference when synthesizing the image when operating as theaccumulation type pixel and the image when operating as the photovoltaictype pixel.

<Overview>

As described above, according to the first and second embodiments, it ispossible to block the diffusion of the signal charge to the adjacentpixel by providing the element isolation region.

Therefore, crosstalk is suppressed in the vicinity of the photovoltaictype pixel and, in the first embodiment, it is possible to dispose thephotovoltaic type pixel and the accumulation type pixel adjacent to eachother without degrading the image quality or the sensitivity.

Furthermore, for example, it is possible to obtain the linear outputimage and the logarithmic output image in the same imaging device bydisposing the photovoltaic type pixel and the accumulation type pixeladjacent to each other without using an optical system that is largescale and expensive such as using a half mirror.

Then, it is possible to obtain the image in a wide luminance range withless noise by obtaining the linear output image and the logarithmicoutput image in the same imaging device without underexposing a lowluminance portion or overexposing a high luminance portion of theobject.

Furthermore, according to the second embodiment, since the same pixelcan be operated as the photovoltaic type pixel and the accumulation typepixel without increasing the dark current, it is possible to synchronizethe image by using the output value of the accumulation type in the lowluminance portion of the object and using the output value of thephotovoltaic type in the high luminance portion of the object.Therefore, it is possible to obtain the linear output image and the logoutput image without sacrificing the resolution.

Furthermore, when calibrating the log output value by using the linearoutput value, it is possible to cancel the change in the temperature ofthe output value of the photovoltaic type by calibrating the outputvalue of the photovoltaic type using the output value of theaccumulation type. Thus, it is possible to reduce the luminance or colorlevel difference in the interface between the linear output image andthe log output image.

Moreover, the first and second embodiments described above can beapplied to any electronic apparatus having an imaging function inaddition to the imaging apparatus represented by a digital camera.

Furthermore, embodiments of the present disclosure are not limited tothe embodiments described above and various modifications are possiblewithout departing from the scope of the present disclosure.

The present disclosure can take the following configurations.

(1) An imaging device including: photovoltaic type pixels that havephotoelectric conversion regions generating photovoltaic power for eachpixel depending on irradiation light; and an element isolation regionthat is provided between the photoelectric conversion regions ofadjacent pixels and in a state of substantially surrounding thephotoelectric conversion region.

(2) The imaging device according to (1), in which the element isolationregion is configured of a material that blocks diffusion of signalcharge of the photovoltaic type pixels to the adjacent pixel.

(3) The imaging device according to (1) or (2), further including: anaccumulation type pixel that is provided in a position adjacent to thephotovoltaic type pixel.

(4) The imaging device according to any one of (1) to (3), in which a PNjunction diode is formed in the photoelectric conversion region as aphoto-sensor.

(5) The imaging device according to any one of (1) to (4), in which thephotovoltaic type pixel further includes a transfer gate and floatingdiffusion and operates as an accumulation type and photovoltaic typepixel.

(6) The imaging device according to (5), further including: anaccumulation type pixel that is in a position adjacent to theaccumulation type and photovoltaic type pixel.

(7) The imaging device according to any one of (1) to (4), furtherincluding: an accumulation type and photovoltaic type pixel having thephotoelectric conversion region, a transfer gate, and floatingdiffusion, in which the photovoltaic type pixel and the accumulationtype and photovoltaic type pixel are formed adjacent to each other.

(8) The imaging device according to any one of (1) to (7), in which aportion between the photoelectric conversion region and a pixel circuitregion in each pixel is insulated.

(9) An electronic apparatus equipped with an imaging device, in whichthe imaging device includes photovoltaic type pixels that havephotoelectric conversion regions generating photovoltaic power for eachpixel depending on irradiation light, and an element isolation regionthat is provided between the photoelectric conversion regions ofadjacent pixels and in a state of substantially surrounding thephotoelectric conversion region.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

REFERENCE SIGNS LIST

-   -   10 Photovoltaic type pixel    -   11 PN junction diode    -   12 Amplifier    -   21 Photoelectric conversion region    -   22 Pixel circuit region    -   31 P-type region    -   32 N-type region    -   33, 34 Electrode    -   35 Element isolation region    -   61 Photovoltaic type pixel    -   62 Accumulation type pixel    -   70 Accumulation type and photovoltaic type pixel    -   71 TG    -   72 FD    -   73, 74 RST    -   75 Sel

What is claimed is: 1-9. (canceled)
 10. An imaging device comprising:photovoltaic type pixels that have photoelectric conversion regionsgenerating photovoltaic power for each pixel depending on irradiationlight; an element isolation region that is provided between thephotoelectric conversion regions of adjacent pixels and in a state ofsubstantially surrounding at least one of the photoelectric conversionregions; and an accumulation type pixel that is provided in a positionadjacent to at least one of the photovoltaic type pixels.